Bassanite Mineral Data

Bassanite Mineral Data +

General Bassanite Information

Chemical Formula:

2CaSO4·(H2O)

Composition:

Molecular Weight = 290.30 gm

Calcium 27.61 % Ca 38.63 % CaO

Hydrogen 0.69 % H 6.21 % H₂O

Sulfur 22.09 % S 55.16 % SO₃

Oxygen 49.60 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

2(Ca)2(SO₄)·(H₂O)

Environment:

In cavities in leucite-tephrite blocks, 1906 eruption. Dehydrates at 130 deg. C. Hydrates to gypsum in a humid atmosphere.

IMA Status:

Valid Species (Pre-IMA) 1910

Locality:

Vesuvius, Italy. Link to MinDat.org Location Data.

Name Origin:

Named for Francesco Basani (185301916). Italian paleontologist, University of Naples, Italy.

Synonym:

Hemihydrate

Plaster of Paris

Bassanite Image

Images:

Bassanite

Comments: White, blocky bassanite crystals on matrix.
Location: Taft, Kern County, California, USA. Scale: Size Not Given.
© Lou Perloff / Photo Atlas of Minerals

Bassanite Crystallography

Axial Ratios:

a:b:c =0.9476:1:0.5461

Cell Dimensions:

a = 12.031, b = 12.695, c = 6.934, Z = 6; V = 1,059.05 Den(Calc)= 2.73

Crystal System:

OrthorhombicSpace Group: Unk

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.006(1), 2.807(0.85), 6(0.7),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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H - Help Screen
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Ballirano P , Maras A , Meloni S , Caminiti R , European Journal of Mineralogy , 13 (2001) p.985-993, The monoclinic I2 structure of bassanite, calcium sulphate hemihydrate

Physical Properties of Bassanite

Color:

Colorless, Snow white.

Density:

2.7

Diaphaniety:

Transparent to Translucent

Habit:

Acicular - Occurs as needle-like crystals.

Habit:

Microscopic Crystals - Crystals visible only with microscopes.

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Bassanite

Gladstone-Dale:

CI meas= -0.038 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.026 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2051,KPDmeas= 0.2074,KC= 0.1999

Optical Data:

Uniaxial (+), w=1.55, e=1.57, bire=0.0200.

Calculated Properties of Bassanite

Electron Density:

r_electron=2.75 gm/cc
note: r_Bassanite=2.73 gm/cc.

Fermion Index

Fermion Index = 0.00226
Boson Index = 0.99774

Photoelectric:

PE_Bassanite= 4.71 barns/electron
U=PE_Bassanite x r_electron= 12.94 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Bassanite is Not Radioactive

Bassanite Classification

Dana Class:

29.6.1.1 (29)Hydrated Acid and Sulfates

(29.6)where A XO4 · x(H2O)

(29.6.1)Dana Group

29.6.1.1 Bassanite 2CaSO4·(H2O) Unk Ortho

Strunz Class:

VI/C.22-10 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/C - Water-bearing sulfates without unfamiliar anions. Cations of very big size

VI/C.22 - Bassanite - Ardealite series

VI/C.22-10 Bassanite 2CaSO4·(H2O) Unk Ortho

VI/C.22-20 Gypsum CaSO4·2(H2O) A2/a 2/m

VI/C.22-25 Rapidcreekite Ca2(SO4)(CO3)·4(H2O) Pcnb 2/m 2/m 2/m

VI/C.22-30 Ardealite Ca2(SO4)(HPO4)·4(H2O) Cc m

Other Bassanite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

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Print or Cut-and-Paste your Bassanite Specimen Label here :

Bassanite

2CaSO4·(H2O)
Dana No: 29.6.1.1 Strunz No: VI/C.22-10
Locality:

Notes: